Page 934 - ABB_Motor _Protection_and_Control_catalogue_20221216

13/44 ABB MOTOR PROTECTION AND CONTROL

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DOL and reversing starters protected by overload relays
With AF contactors - Open type version in kit form
Switching frequency diagrams

General
Overload relays cannot be operated at any arbitrary switching frequency in order to avoid tripping. Applications involving up
to 15 operations per hour are acceptable. Higher switching frequencies are permitted if the duty ratio and the motor start-
ing time are allowed for and if the motor's making current does not appreciably exceed 6 times the rated operating current.
Please refer to the adjacent diagram for guideline values for the permitted switching frequency.

Thermal overload relay
Intermittent periodic duty Example:

(Op/h)
Switching frequency (ops/h) switching frequency 120 t = 1.5 s t = 0.5 s Starting time of the motor: 1 second - Duty ratio: 40 % means a
140
permitted switching frequency of max. 60 operating cycles per hour.
100
a
80
a
60
a
t = 1 s
40
a
20
a
t = 5 s
0 t = 3 s
0 20 40 60 80 100 (%)
duty ratio
Duty ratio (%)
ta: motor starting time
Electronic overload relay

Intermittent periodic duty
Trip class 10E Trip class 20E Trip class 30E
(Op/h) t = 5 s Trip class 30E
50
Trip class 10E
(Op/h)
Trip class 20E
(Op/h)
Switching frequency (ops/h) switching frequency 140 t = 1 s Switching frequency (ops/h) switching frequency 70 t = 4 s Switching frequency (ops/h) switching frequency 35 t = 10 s
a
45
a
160
80
40
t = 0.5 s
a
t = 2 s
120
60
30
50
100
25
a
a
80
40
20
a
30
15
60
a
a
t = 1.5 s
t = 15 s
a
t = 6 s
40
a
a
t = 20 s
t = 8 s
a
a
10
a
20
a
t = 5 s
a
t = 12 s
20
20
0 t = 3 s 20 0 0 t = 10 s 40 60 80 100 (%) 10 5 0 0 t = 25 s 40 60 80 100 (%)
0 20 40 60 80 100 (%) duty ratio
duty ratio duty ratio
Duty ratio (%) Duty ratio (%) Duty ratio (%)
ta: motor starting time
Exemple for trip class 10E:
Starting time of the motor: 1 second. Duty ratio: 60 % means a permitted switching frequency of max. 60 operating cycles
13
per hour, for a motor breaking current not exceeding 6 x In.